Single serving metal beverage containers such as soda or beer cans are currently marketed with self contained openers in the form of lift tabs. In all of the present embodiments, the lift tab is comprised of a ring-like lift portion for control by an inserted finger. In one form of lift tab, the ring is attached to a pear shaped pre-scored section of the container top, with continued lifting of the ring causing a relatively large pear shaped section to become completely detached from the container top. This type of lift tab has however met with an environmental outcry since it has resulted in a new type of litter. Accordingly, a more acceptable non-detachable lift tab is presently being utilized on nearly all of the soda and beer cans currently sold in the United States, with the soda and beer cans being themselves recycled to reduce litter.
However, unlike the containers with removable tabs which provided large openings and thereby permitted relatively easy drinking directly from the container, the non-detachable lift tabs impede direct drinking. The opening made with the non-detachable lift tab is, of necessity, relatively small and close to the rim of the container. Direct drinking results in the entire opening being covered by the mouth, thereby causing the contained beverage to flow out in a trickle rather than a strong flow. In addition, the tab itself obstructs drinking access to the opening. As a result, drinking from the container is in the form of a less than satisfying dribble. To obviate these disadvantages, the drink is either poured into a second container such as a cup, or straws are inserted into the opening.
The non-detachable lift tab, with some design variations, is basically comprised of a short, somewhat rectangular, elongated aluminum strip (about 11/8.times.5/8inch--28.times.16 mm) with rolled over edges for structural strength and for prevention of exposed sharp edges. At a first end, the tab is formed into a ring-like member (also with rolled over inner edges) for finger insertion and lifting. The second end, with strengthened rolled over edge, is rounded or tapered and centrally crimped for force-concentrated pushing engagement with a cantilevered weakened section of the container top, which will open upon continued application of force.
To facilitate manufacture and container storage nesting, the usually circular container top is shallowly dished along a major portion of a diameter thereof. About half of the length of the dished area is formed for seated mating with the lift tab, i.e., slightly larger but conformed to the peripheral shape of the lifting end and adjacent sides of the lifting tab. The center of the container top, situated within the dished area, is formed with an integral outwardly extending hollow rivet-like section which fits into a corresponding aperture located on the longitudinal axis of the tab. The aperture is positioned on the tab such that the engagement between tab and container top results in about three quarters of the length of the tab (the lifting end) being situated on one side of the engagement site and about one quarter of the tab (the pushing end) being situated on the other side. The rivet-like section is then peened over, during assembly, to fixedly attach the lift tab to the container top.
The remaining dished area in the container top contains a peninsularly shaped weakening score line such as in the shape of a thumb nail (other similar design related shapes include truncated ovals or circles) having its tapered (or arced) end extending in a direction away from the tab. A small portion of the "thumb nail", peripherally adjacent to the engagement site, however remains unscored. The pushing end of the tab extends over the non-scored portion and over the adjacent area enclosed by the thumb nail score line. During the opening operation, the lifting end of the tab is elevated. The tab pivots through the rivet engagement area and the pushing end of the tab swivels down thereby tearing the scored section and pushing the weakened area of the container top into the container. Because of its proximity to the pushing end of the tab, the scored area, adjacent the rivet-like section, tears open first, with initial internal gas pressure relief (the contained beverages are usually carbonated or are susceptible to internal gas evolution).
Upon continued pushing force, the tear propagates around the score line away from the pushing end of the tab. The section of the container top, enclosed by the score line, then pivots down into the container in a cantilevered movement, and is held from falling into the container by the small unscored section of the "thumb nail". The area surrounding the contact point between the tab end and the container top is strengthened by a raised rib integrally formed within the "thumb nail" area to prevent gouging of the container top by the tab end.
Several embodiments of prior art containers include frangible buttons or sections of the container which are initially pressed either with a finger or by depression of the tab with a finger. These buttons or frangible sections pop to provide initial pressure relief for facilitated opening of the container. However, in order for such buttons or frangible sections to be effectively opened by finger pressure, a portion of a pressurized container must be overly weakened. The weakened section is, however small, to avoid undue weakening of the container, and since only a small opening is required for pressure relief.
Inclusion of the pressure relief sections, requires expensive modification of existing machinery for producing beverage cans, to form the can tops with integral buttons or frangible sections. Manufacturers are accordingly very reluctant to effect such modifications, particularly since the necessity for the initial pressure relief has been substantially obviated by use of the container-opening lift tabs, which, upon initial use, allow for the pressure relief.
Most detrimentally, such buttons or frangible sections operate with the tab being depressed against the button or frangible area. This depression often occurs simply upon handling of the containers and the buttons or frangible sections are readily accidentally activated during handling of the containers. For these reasons their use has been avoided.